Multistage power load

ABSTRACT

A conventional cartridge with primer contains a two stage explosive charge consisting of an explosive powder primary charge and a solid propellant booster charge. The explosive force capability of the booster charge is at least about 15 percent that of the explosive powder and the ignition of the booster charge takes place at a distinct time interval after the explosion of the primary charge.

United States Patent Hsu 1 Mar. 14, 1972 [54] MULTISTAGE POWER LOAD 2,299,464 10/1942 Coffman ..102/40 3,372,643 3/l968 Kvavle [72] invent Shins 3,435,170 12/1969 Scanlon 102/38 I [73] A'ssignee Omark ndustnes, luc Portland Oreg FOREIGN PATENTS OR APPLICATIONS [22] Sept 1969 9,870 4/1907 Great Britain ..102/40 [211 App]. No; 856,792

Primary Examiner-Robert F. Stahl rt 11 [52] us. c1... ..1o2/40, 102/42 Mame Lyle amngm [51] Int. Cl ..F42b 7/02, F42b 9/ 1 4 l 57] ABSTRACT [58] Field of Search ..102/40, 38, 99, 43 C, 42, DIG. 1

A conventional cartridge with primer contains a two stage ex- [56] References Cited plosive charge consisting of an explosive powder primary charge and a solid propellant booster charge. The explosive UNITED STATES PATENTS force capability of the booster charge is at least about 15 percent that of the explosive powder and the ignition of the 389,496 9/1888 Brovvn ..102/40 booster charge takes place at a distinct time interval after the 694,295 2/1902 explosion of the primary charge. 702,664 6/1902 Mattson. 751,519 2/1904 Kilzer 102/40 5 Claims, 6 Drawing Figures Patented- March 14, 1972 z 7 m M K 5 u,

MULTISTAGE POWER LOAD HISTORY OF THE INVENTION This invention relates to power loads such as used in explosively actuated construction tools, fire arms and the like.

Power loads as contemplated herein refers to devices containing an explosive material which is adapted to be exploded in a manner whereby a'thrust force is produced to propel an object. Such a power load is commonly ignited in some form of a tool having means for causing explosion of the explosive material with the resulting force being released down a barrel which directs the force against the object.

Tools capable of safely handling such power loads become more complicated, more expensive and subject to much greater control at a fast incline as the peak explosive pressure of the power load becomes higher. However, with prior power loads having but a single stage explosive charge, the thrust power is in direct relation to the peak-explosive pressure. Thus heretofore increasing the thrust power meant increasing the peak-explosive pressure which in turn meant the use of stronger and more expensive tools with increased handling restrictions.

It is an object of the present invention to provide a power load with improved thrust power to explosive peak pressure ratio. This is accomplished in the preferred embodiment of the invention by providing a two stage explosive charge created by primary and secondary ignition of two distinct explosive materials. This successive explosion of the dual power load materials results in a greater time interval of peak or near peak-explosive pressure. A total thrust power is achieved that could be accomplished only with a significantly greater peakexplosive pressure of a single power load-explosive material.

A power load of the present invention is briefly described in the Abstract. The improved results of this structure indicates that upon explosion of the primary charge the booster charge is initially set in motion but then ignites at a very short but distinct time interval after the primary explosion. It is theorized, although applicant does not wish to be bound by such theory, that the high compression created behind the booster charge and the forward motion imparted to it causes the subsequent or secondary thrust force generated by the explosion of the booster charge to be concentrated in the direction of movement. This theory appears supported by the spent cartridge showing definite signs of collapse which would not seem to occur if a significant backward force were generated by the secondary explosion. It follows that the spent cartridge is then easily removed from the chamber.

Other advantages will be apparent by referring to the following detailed description and drawings wherein:

FIGS. 1 through 4 show in cross section a power load of the present invention in position in the firing chamber of a schematically illustrated tool with step-by-step illustrations of the two stage ignition of the dual power charge;

FIG. 5 illustrates a second embodiment of the invention;

FIG. 6 illustrates a third embodiment of the invention;

Referring to FIGS. 1 thru 4, partially illustrated is a tool 10 such as may be used in numerous applications, for example, in the construction tool industry where explosive-actuated tools are used to drive fastening studs into concrete walls, and for example in the meat-packing industry where explosive-driven rams are used to stun cattle for slaughtering. It is to be understood however that the tool is shown only schematically to illustrate the performance of an exploded power load of the invention.

A power load 14 includes a cartridge consisting of a discshaped base pad and a tubular wall 18 extending from and integral with said base pad 20. An explosive powder 22 is contained within the tubular wall 18 adjacent the base pad 20. The tubular section within the cartridge occupied by the explosive powder 22 is hereafter sometimes referred to as the bottom section of the cartridge. Adjacent the explosive powder opposite the base pad 20 is unified cylindrical solid propellant booster charge 24. This booster charge is formed from an explosive material compressed into a unified mass and assuming the approximate dimensions of the interior of the tubular wall. The booster charge is utilized to pack the explosive powder 22 as desired while sealing the explosive powder from the open end of the tubular wall 18. The outer end of the tubu lar wall 18 is roll crimped as shown in FIGS. 1 and 2 to hold the booster charge 24 within the cartridge. However, it will be understood that other means may be used for holding the booster charge within the cartridge the function of which is described later.

The cartridge of the power load 14 as generally described above is preferably made from a metal such as brass and is similar in construction to the cartridges used in conventional power loads. Such cartridges are well known to the industry and no further explanation thereof is deemed necessary.

The explosive power 22 can be generally referred to as stabilized nitrocellulose granules. This material is used in conventional power loads and is also well known to the industry. No detailed disclosure is believe necessary. The booster charge is a unified mass as for example provided by compacting nitrocellulose fibers into a density of about 1.30 to L40 grams per cubic centimeter. The booster charge is preferably sufficiently unified so that it can withstand substantial abuse without breaking. One form of unified nitrocellulose fibers is described in U.S. Pat. No. 3,372,643 issued Mar. 12. I968.

The use of a combustible wad for a power load was suggested many years ago in a patent issued to Walter O. Snelling, U.S. Pat. No. I,9l7,988 dated July I I, 1933. Snelling employed a thin disc of explosive material as a wad and claimed that the burning of the wad upon explosion of the power load minimized contamination of the tool while increasing explosive efficiency. While these advantages are also realized in the present invention, the structure of the power load of the present invention is distinguished from Snelling in a very important respect. By providing a unified booster charge having an explosive capability that is a significant portion of the total explosive charge of the power load, it is found that the ignition and burning of the booster charge does occur simultaneously with the explosive powder. The compact mass of the booster charge is sufficient to resist simultaneous ignition until a distinct time interval latter resulting in a primary and secondary thrust power as demonstrated in FIGS. 2 thru 4.

FIG. 2 illustrates firing pin 28 of the tool 10 having been released to strike a primer 26 located in the base pad 20 of the cartridge. It is to be understood that the location of the primer in the base pad is shown for demonstration purposes only. In actual practice the primer is frequently located in the rim of the base pad 20.

FIG. 3 illustrates the ignition of the explosive powder 22 caused by the primer with the initial effect being to urge the booster charge forward. This forward movement is initially resisted by the partially closed end caused by the roll crimp. Upon buildup of pressure the crimped end is unrolled to fully open the end of the cartridge and the booster charge propelled forward. The rapid buildup of heat and pressure, caused at least in part by the primary explosion being confined by the initial resistance of the roll crimp, very quickly reaches the point of igniting the propelled booster charge creating the secondary explosion as illustrated in FIG. 4. The total thrust power is directed against a power ram 16 slidably contained within the tool. The power ram is then propelled at a high speed to create an impulsive force as for example to drive a fastening pin (not shown). Although oceuring very quickly after the primary explosion the peak-explosive pressure of the secondary explosion occurs at a point in time when the initial peak-explosive pressure has at least partially subsided.

The cumulative effect of the double explosion is to maintain a high-peak explosive pressure at or near the maximum over a greater time interval. It is believed that the above desired result is achieved only by providing a unified explosive mass that significantly resists ignition so that explosion does not occur simultaneously with the primary explosion. Also the mass must have sufficient explosive capabilities to create an effective secondary or booster thrust power. lt has been determined that the desirable results of the invention are realized with the booster charge 24 having explosive capabilities at least about fifteen percent (l5%) that of the explosive powder.

l-"IG. 5 of the drawing illustrates a second embodiment of the invention and represents a cartridge 40 used as ammunition for fire arms. The cartridge of the power load is comprised of a base pad 44 with tubular wall 42. explosive powder 46 contained in the lower section, a booster charge 48 over the explosive power and a slug 49 positioned in the top of the partridge. The firing of the cartridge 40 occurs in the same manner and with the same desireable effects explained in connection with FIGS. 1 thru 4 except that the thrust power is directed to propel the slug down the barrel of a fire arm.

FIG. 6 illustrates a third embodiment of the invention and represents a power load for a shotgun shell 50. The cartridge pf the shotgun shell is comprised of a conventional base pad with primer S6 and a tubular wall 52. An explosive powder 54 is enclosed in the bottom section of the shell by a booster charge 60. Contained in the shell above the booster charge is a quantity of shot 58. Again the power load is ignited and exploded in two stages to produce the desired improved thrust power for propelling the short 58 out of the shell.

Numerous other embodiments and modifications having a variety of applications will be apparent to those skilled in the art without departing from the invention. Thus it is intended that the scope of the invention [5 not to be limited by the above described illustrations but encompasses the scope afl'orded by the by the appended claims.

Having thus described the invention what is claimed is:

l. A cartridge having means for directing the force of an explosive to propel an object. said cartridge comprising; a

all 115 generally tubular noncombustible casing having a closure at one end; a powdered explosive confined within the casing adacent said closed end; a unified one-piece propellant booster charge having a peripheral size and shape substantially equal to the internal size and shape of said casing, seated adjacent said propellant powder and confining said powder with said casing; said booster charge of sufficient explosive force to equal at least the explosive force of IS percent of the powdered explosive, and means in said closure for exploding the powdered explosive to create a primary explosion. and said booster charge being compressed so as to resist instantaneous ignition from said primary explosion thereby creating a delayed secondary explosion.

Z. A cartridge as defined in claim 1 wherein the powdered explosive is comprised of stabilized nitrocellulose granules and the booster charge is comprised of compacted nitrocellulose t'ibers having a density of about 1.30 to 1.40 grams per cubic centimeter.

J. A cartridge as defined in claim 1 wherein said means for exploding the powdered explosive is comprised of a primer at the closed end of the casing and the end of the casing opposite said closed end being roll crimped over the booster charge for containing the charge in the casing prior to explosion.

4. A cartridge as defined in claim 1 including a slug contained in the casing over the booster charge that is propelled by the cumulative primary and secondary explosions down the barrel of a conventional firearm.

5. A cartridge as defined in claim 1 including a quantity of shot contained in the casing over the booster charge that is propelled by the cumulative primary and secondary exploilOflS down the barrel of a conventional shotgun.

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2. A cartridge as defined in claim 1 wherein the powdered explosive is comprised of stabilized nitrocellulose granules and the booster charge is comprised of compacted nitrocellulose fibers having a density of about 1.30 to 1.40 grams per cubic centimeter.
 3. A cartridge as defined in claim 1 wherein said means for exploding the powdered explosive is comprised of a primer at the closed end of the casing and the end of the casing opposite said closed end being roll crimped over the booster charge for containing the charge in the casing prior to explosion.
 4. A cartridge as defined in claim 1 including a slug contained in the casing over the booster charge that is propelled by the cumulative primary and secondary explosions down the barrel of a conventional firearm.
 5. A cartridge as defined in claim 1 including a quantity of shot contained in the casing over the booster charge that is propelled by the cumulative primary and secondary explosions down the barrel of a conventional shotgun. 